The disclosure of Japanese Patent Application No. 2002-067454 filed on Mar. 12, 2002 including the specification, drawings and abstract is incorporated herein by reference in its entirety.
1. Field of the Invention
The present invention relates to an apparatus and a method for evaluating damping performance or capability of vibration-damping devices, and to a testing method using the apparatus.
2. Description of the Related Art
A variety of vibration-damping devices using elastic members or the like have been employed or proposed in order to reduce vibration excited in apparatus and equipments of various kinds in which vibration would raise problems. The proposed vibration-damping devices have a variety of constructions including a so-called dynamic damper as disclosed in JP-A-8-193642 and a vibration-damping device as disclosed in WO00/14429, which are arranged in order to reduce vibrations and noises within the vehicle caused by oscillation force transmitted from a power unit, tires, and the like.
The dynamic damper taught by JP-A-8-193642, the vibration-damping device disclosed in WO00/14429, and similar devices may not always effectively exhibit the desired damping performance, due to deviation in factors such as component dimensions, materials and mass.
To ensure that final products consistently exhibit required damping performance, it is desirable to subject vibration-damping devices to performance evaluation testing prior to shipment. Specific examples of testing methods include, for example, (a) sweep oscillation methods, which involve subjecting the vibration-damping device to vibrational load at gradually varied frequency with an electromagnetic vibrator while measuring vibrational input/output characteristics in terms of phase angle, gain etc; and (b) hammering methods, which involve measuring vibrational characteristics including resonance frequency or other intrinsic values, while subjecting the vibration-damping device to impact force.
The former one, (a) sweep oscillation methods, have the disadvantage of high cost of testing equipment per se, as well of requiring some time for the vibration mode of the vibration-damping device to stabilize so that the total time required for a single test cycle, including installation and removal of the vibration-damping device in and from the testing device, can be as long as 120 seconds. For this reason, the sweep oscillating methods are impractical where all or virtually all of the final product units are to be tested. The latter case, (b) hammering methods, on the other hand, while affording shorter measuring times than sweep methods, have the drawback that due to the extreme difficulty of consistently controlling parameters such as the magnitude and direction of the impact force during measurement, the benchmark for evaluating damping performance is not always precise vis-xc3xa1-vis the actual measurements obtained, so that these measurements can only be used as a general guide.
It is therefore an object of the present invention to provide a novel damping performance evaluation apparatus and damping performance evaluation method for vibration-damping devices whereby damping performance of vibration-damping devices can be measured quickly and with high accuracy, and a novel testing method for vibration-damping devices, which employs the vibration performance evaluation apparatus.
The above and/or other objects may be attained according to at least one of the following modes of the invention. Each of these modes of the invention is numbered like the appended claims and depending from the other mode or modes, where appropriate, to indicate possible combinations of elements or technical features of the invention. It is to be understood that the following modes or elements of the invention may be adopted at any possible optional combinations, and that the present invention is not limited to the following modes or combinations of these modes, but may otherwise be recognized based on the thought of the present invention that described in the whole specification and drawings or that may be recognized by those skilled in the art in the light of the disclosure in the whole specification and drawings.
(1) A damping performance evaluation apparatus for vibration-damping devices comprises: (a) a support member for detachably supporting a vibration-damping device in a state enabling the vibration-damping device to exhibit a damping effect thereof; (b) a hammer member for applying oscillation force to the vibration-damping device, caused by means of gravitational action to descent to strike directly or indirectly the vibration-damping device supported by the support member; (c) a double-strike preventing member for preventing the hammer member from dropping a second time due to rebound after initially striking the vibration-damping device, so as to prevent double-strike of the vibration-damping device by the hammer member; (d) a vibration sensor installed at a vibration zone caused to vibrate through oscillation force applied by the hammer member, for outputting an electrical signal in response to vibration at the vibration zone; and (e) a sensing member for sensing a vibration mode in the vibration zone on the basis of an output of the vibration sensor.
The damping performance evaluation apparatus constructed according to this mode of the invention is designed to allow damping performance of the vibration-damping device to be evaluated by applying oscillation force to the vibration-damping device while supported in the state enabling the device to exhibit damping effect. This is accomplished by causing the hammer member to undergo gravitational descent and strike the vibration-damping device directly or indirectly, and then measuring, by means of the vibration sensor and the sensing member, the vibration mode in the vibration zone caused to vibrate through oscillation force applied by the hammer member.
By means of the double-strike preventing member, the hammer member is prevented from dropping the second time due to rebound after initially striking the vibration-damping device, thus preventing double-strike of the vibration-damping device by the hammer member. This permits the vibration-damping device to be subjected to one cycle of a given level of initial oscillation force through gravitational action. Thus, in the initial stage of vibration, the vibration zone can be impacted consistently with oscillation force of constant magnitude and directionality, so as to provide uniform conditions for measurement over multiple tests. Measurements for a number of vibration-damping devices can thus be evaluated on the basis of a consistent benchmark, making it possible to judge damping performance satisfactory or unsatisfactory with a high degree of accuracy.
As a general principle, a single application of oscillation force through gravitational action to the vibration-damping device is enough to complete the measuring procedure, thereby allowing the vibration mode in the vibration zone to be measured quickly, so that testing of all vibration-damping device units prior to shipment, for example, is now viable.
A variety of know sensors those employing a piezoelectric element to output an electrical signal may be preferably employed as the vibration sensor in the present mode, for example. The sensing member may be suitably designed depending upon items of damping performance being evaluated, using, for example, an analog or digital level recorder, band pass filter, tracking filter, frequency analysis device, or the like. Preferably, a frequency analyzer employing a Fast Fourier Transform (FFT) is employed, for the sake of rapidity of measurement and ease of modifying measurement settings.
(2) A damping performance evaluation apparatus according to the above mode (1) further comprises hammer supporting mechanism for supporting the hammer member at a predetermined height, and for releasing the hammer member so as to allow the hammer member to descend under the gravitational action. The damping performance evaluation apparatus constructed according to this mode of the invention is capable of readily applying consistent oscillation force to vibration-damping devices to be evaluated.
(3) A damping performance evaluation apparatus according to the above mode (2) further comprises a lift driving device for lifting the hammer member against gravitational force and causing the hammer member to be supported at predetermined height by the hammer supporting means. This mode of the invention permits a simpler procedure for evaluating damping performance of the vibration-damping devices in comparison with the case where, for example, the hammer member is lifted manually to support it on the hammer supporting mechanism, and further facilitates automation of the evaluation process.
(4) A damping performance evaluation apparatus according to any one of the above modes (1)-(3), wherein the double-strike preventing member comprises (f) a rebound detection member for detecting displacement of the hammer member due to the rebound after initially striking the vibration-damping device and (g) retaining mechanism, actuated on the basis of the output of the rebound detection member, for retaining the hammer member rebounded after initially striking the vibration-damping device. The damping performance evaluation apparatus constructed according to this mode of the invention is designed so that displacement of the hammer member due to the rebound after initially striking the vibration-damping device is detected by the rebound detection member, and the retaining mechanism is actuated on the basis of the output of the rebound detection member in order to retain the hammer member as it rebounds after initially striking the vibration-damping device, thus making it possible to prevent the hammer member from dropping a second time. Double-strike of the vibration-damping device by the hammer member is thus effectively prevented.
The rebound detection member in this mode of the invention may comprises, for example, a limit switch or other element for detecting or sensing displacement of the hammer member through contact with the hammer member. Preferably, it is employed a non-contact element capable of detecting or sensing displacement of the hammer member without actually contacting the hammer member, such as an encoder, a proximity switch, a photoelectric switch, or the like. The retaining mechanism may be designed as any means or mechanism capable of releasably preventing the hammer member from falling. Examples of the retaining mechanism include a member or mechanism that retains the hammer member through mechanical grasping or magnetic attraction, or that retains the hammer member through friction or engaging force.
(5) A damping performance evaluation apparatus according to any one of the above modes (1)-(4), further comprises an arm member rotatably supported about a single axis, wherein the hammer member is fixed to an distal end of the arm member, and the arm member is rotatable about the single axis to support the hammer member at the predetermined height, and then to allow the hammer member to descend under gravitational action to strike directly or indirectly the vibration-damping device supported by the support member. The damping performance evaluation apparatus constructed according to this mode of the invention enables the arm member having the hammer member fixed to its distal end to be rotated about the single axis to thereby support the hammer member at the predetermined height, whereby a generally constant level of oscillation force applied by the hammer member dropping under the action of gravity may be readily achieved, by means of simple construction. In preferred practice, the present mode (5) will be combined with the above-described mode (3), in which case it will be advantageous for the lift driving device to comprise rotary actuating means or members for actuating the arm member about the single axis.
(6) A damping performance evaluation apparatus according to the above mode (5), further comprises a supplemental mass formed independently of the hammer member and attached to the arm member. According to this mode of the invention, the use of the supplemental mass makes it possible to readily reset magnitude of oscillation force produced by the hammer member. Described in detail, when the supplemental mass is attached to one side of the arm member opposite to the other side provided with the hammer member, with the center axis of rotation of the arm member disposed therebetween, the magnitude of the oscillation force produced by the hammer member can be decreased. When the supplemental mass is attached to the other side of the arm member to be interposed between the hammer member and the center axis of rotation of the arm member, on the other hand, the magnitude of the oscillation force produced by the hammer member can be increased.
(7) A damping performance evaluation apparatus according to any one of the above modes (1)-(6), wherein the vibration sensor is detachably attachable to the vibration zone by means of a magnet. The damping performance evaluation apparatus constructed according to this mode of the invention allows the vibration sensor to be attached and detached easily, thus further reducing a period of time needed for measurement.
(8) A damping performance evaluation apparatus according to any one of the above modes (1)-(7), wherein the apparatus is adapted to evaluate a damping performance of at least a vibration-damping device that constitutes a secondary vibration system wherein a damper mass is elastically supported on a damping target via a spring member, the vibration-damping device being supported by means of the support member at an mounting part thereof on the damping target, and the hammer member being caused to strike the vibration-damping device directly or indirectly to apply the oscillating force to the vibration-damping device. The damping performance evaluation apparatus constructed according to this mode of the invention is capable of suitably evaluating damping performance of such a vibration-damping device that constitutes the secondary vibration system attached to the damping target as the primary vibration system, and may also be usable for evaluating damping performance of a variety of dynamic dampers known in the art, for example.
(9) A damping performance evaluation apparatus according to the above mode (8), wherein the damper mass includes a rigid abutting portion and an independent mass member disposed on the rigid abutting portion such that the independent mass member is uncoupled from and independently displaceable relative to the rigid abutting portion, and that the independent mass member is brought into direct and elastic abutting contact with the rigid abutting portion in a direction of input of vibration to be damped. In the vibration-damping device to be evaluated by the damping performance evaluation apparatus constructed according to this mode of the invention, the arrangement of the independent mass member that controls damping performance of the vibration-damping device is not easily visible from the outside. However, the use of the damping performance evaluation apparatus constructed according to this mode of the invention makes it possible to easily carry out damping performance evaluation of such a vibration-damping device having a specific construction of this kind. Described in detail, where the abutting portion is a hollow housing having an interior space and the independent mass member is housed within the housing, for example, it may be difficult to ascertain from the outside whether the independent mass member is housed within the housing or whether the independent mass member comes into impact on the housing during input of vibration. However, the present damping performance evaluation apparatus makes it possible to readily ascertain whether the vibration-damping device has been manufactured to design standards and exhibits the desired damping effect.
(10) A damping performance evaluation apparatus according to any one of the above modes (1)-(7), the apparatus being adapted to evaluate a damping performance of at least a vibration-damping device including an abutting member fixable to a damping target and an independent mass member disposed on the abutting member such that the independent mass member is uncoupled from and independently displaceable relative to the abutting member, and that the independent mass member is brought into direct and elastic abutting contact with the abutting member in a direction of input of vibration to be damped, wherein an elastically deformable support member is provided in the support member, the abutting member of the vibration-damping device is fixed to the elastic support member, and oscillation force is applied to the vibration-damping device by directly or indirectly striking the abutting member with the hammer member. Like the above mode (9), the vibration-damping device to be evaluated by the damping performance evaluation apparatus constructed according to this mode of the invention suffers from difficulty in determining visually from the outside whether the device is good or defective. However, the use of the damping performance evaluation apparatus constructed according to this mode of the invention makes it possible to easily determine whether a unit is good or defective by means of performance evaluation, irrespective of invisibility of condition of the independent mass member.
(11) A damping performance evaluation method for vibration-damping devices comprises: (a) a vibrating step wherein a hammer member is dropped from a predetermined height under gravitational action to directly or indirectly strike a vibration-damping device and apply oscillation force to the vibration-damping device; (b) a double-strike preventing step wherein double-strike of the vibration-damping device with the hammer member is prevented by preventing the hammer member from dropping a second time upon rebound after initially striking the vibration-damping device; (c) a vibration measuring step wherein vibration mode in a vibration zone vibrated by means of the oscillation force of the hammer is measured; and (d) a sorting step wherein vibration-damping devices are sorted into good products and defective products on the basis of the results of measurement in the vibration measuring step.
According to the damping performance evaluation method of the present invention, the step (a) permits an application of the oscillation force to the vibration-damping device, and the step (b) permits a prevention of double-strike of the vibration-damping device with the hammer member, whereby it is possible to strike the vibration-damping device a single time with the hammer member dropped from a given height under gravitational action. This makes it possible to give the vibration zone consistently with oscillation force of constant magnitude and directionality, in the initial stage of vibration.
As a result, uniform conditions for measurement can be provided over multiple tests, so that measurements for a number of vibration-damping devices can be evaluated on the basis of a consistent benchmark. Vibration-damping devices can thus be separated into good and defective units in the step (d), on the basis of the measurements taken in the step (d).
(12) A vibration-damping device testing method wherein a damping performance evaluation method defined in the above-indicated mode (11) is implemented using a damping performance evaluation apparatus defined in any one of the above-indicated modes (1)-(10), at a point between production and shipment of vibration-damping devices.
According to the vibration-damping device testing method of the present invention, vibration modes of vibration zones can be measured quickly, so that all or nearly all manufactured vibration-damping devices can be tested at a suitable point between production thereof and shipping from the factory. This makes it possible to improve performance and reliability in shipped vibration-damping devices, while avoiding adverse effects on production costs and manufacturing efficiency during production of vibration-damping devices.